Thermal damper for plate type heat exchangers

ABSTRACT

A heat exchanger is described which is particularly adapted for use with a regenerative type gas turbine engine. The heat exchanger comprises a series of annular discs which define a central flow path for the hot gas discharge of the engine. Adjacent plates define radial flow paths for the hot gas discharge which alternate with cross flow paths between plenums which are respectively connected to the engine&#39;&#39;s compressor and combustor thereby increasing the energy level of the hot gas stream generated in the combustor. This stack of plates is connected to a frame member of relatively large mass through a series of thermal damper discs which are alternately connected, by seam welding, peripherally around their inner and outer diameters and then peripherally around openings which define the plenum passageways for the flow of air from the compressor and back to the combustor.

Stein et al.

[ THERMAL DAMPER FOR PLATE TYPE Primary Examiner-Charles J. Myhre HEATEXCHANGERS Assistant Examiner-Theophil W. Streule, Jr. [75] Inventors:Wolfgang J. Stein, Milford; Attorneyncharles Hogan et gzgzfitoreStu-amt], Orange, both of 57] ABSTRACT h A heat exchanger is describedwhich is particularly Asslgnee? Avco Corpqratwn, Stratford, Connadaptedfor use with a regenerative type gas turbine [22] Filed: No 15 1972engine. The heat exchanger comprises a series of annular discs WhlChdefine a central flow path for the hot PP 306,968 gas discharge of theengine. Adjacent plates define radial flow paths for the hot gasdischarge which alter- 52 U.S. c1 165/76, 165/80, 165/166 i cmss PathSPlan"ms which are [51] Int. Cl F28f 7/00 respectwely connected to theengmes compressor and [58] Field of Search .L 165/164-167, 157, 170cmbustr hereby iwetsing the energy level. the hot gas stream generatedin the combustor. ThlS stack of plates is connected to a frame member ofrelatively [56] References Cited lalrlgehmass ltthroughl a seriestotgjtllijermal damlpjer discs w 1c are a erna e y connec e y seam wemg, pe- UNITED STATES PATENTS ripherally around their inner and outerdiameters and 3,228,465 l/19 66 Vadot 165/167 then peripherally aroundopenings which fi the 12:23 et plenum passageways for the flow of airfrom the com- 3:603:38] 9 1971 scherbaiiiii 1:............:::Ill:.. 16580 Press and back to the combusm 8 Claims, 4 Drawing Figures Al ll 1 IIII II l lllll Ill llj R FROM COMPRESSOR lllllllillllllllll ll 27 26 HOTGAS f m a DISCHARGE P I 1111 11111 1111111\|11-||| AIR TO COMBUSTOR 22 YL l I l I II II I l l EXHAUST 1 [FEED I II II l llH II I II MF S SOR 20Hl! lllll llll I" PAIENIEUJAN I W 3.785.435

ExFiAusT 24 PAIENTEUJAM I 5 I974 SHEET 2 BF 3 EDIE The present inventionrelates to heat exchangers and more particularly to improvements inmounting plate type heat exchangers.

A particularly effective type of heat exchanger,

adapted for a regenerative type gas turbine engine, is

disclosed in US. Pat. No. 3,424,240. In that heat exchanger, a stack ofcorrugated annular discs defines a central entrance passageway for thehot gas discharge of the engine. The hot gasses pass radially betweenalternate pairs of discs to a discharge duct. Compressor air enterslongitudinally extending plenums and then passes through cross flowpaths between other alternate discs to exit plenums connecting with theengines combustor. The discs are corrugated to facilitate the exchangeof heat from the hot gas stream to the compressor air passing throughthe heat exchanger. In the regenerative type engine, the waste heatenergy of the engine is transferred to the pressurized air in transitbetween the compressor and combustor of the engine. Transfer of heat inthis fashion increases the theoretical efficiency of the engine.

A problem of particular significance is found in mounting such a heatexchanger. The heat exchanger is disposed downstream of the last turbinestage of the engine and must be secured in some fashion to the engineitself. Thus, the thin disc of the heat exchanger, in some fashion, mustbe secured to a relatively massive frame element which will surround thedischarge flow path of the engine and usually include passagewaysconnecting the plenums of the heat exchanger at the compressor and thecombustor of the engine.

The thin corrugated discs of the heat exchanger are secured together bewelding or the like in bellows fashion. Such discs being alternatelyjoined at the inner and outer peripheries and peripherally of openingswhich define the referenced plenums. These thin discs have a high rateof. thermal growth,-as compared to the frame member to which they mustbe joined. During thermal transients a problem arises after repeatedthermal cycles, as encountered in normal engine operation, of a failureat or adjacent the juncture between the discs and the frame. Such afailure can then lead to, leakage between the separate flow paths forthe hot gas discharge and the pressurized air. Such leakage can lead tolosses in engine efficiency or even engine failure.

Accordingly, the object of the invention is to provide an improvedconnection between relatively thin, flow path defining discs, or plates,of a heat exchanger and a mounting frame therefor and more specificallyto devise such an improved mounting for heat exchanger discs having anannular configuration.

The above ends, in accordance with the broader aspects of the invention,are attained by a heat exchanger comprising aseries of relatively thinplates which define alternate flow paths for different fluids betweenwhich heat energy is to be exchanged. This series of plates is connectedto a frame of relatively large mass and low rate of thermal growththrough a thermal damper comprising a series of thermal damper plateswhich are successively connected to each other with the connection toeach thermal damper plate, on opposite sides thereof, being laterallyspaced.

Further, it is advantageous that the thermal damper plates have theiropposite adjacent surfaces in substantially contiguous relationship andalso that the thermal damper plates adjacent the frame have a greaterthickness than those adjacent the heat exchanger plates.

In a configuration particularly adapted for use with a regenerative typeengine, the heat exchanger plates and the thermal damper plates are inthe form of annular discs defining a central passageway for one of thefluids which would be the hot gas discharge of the engine. Further, theheat exchanger discs and the thermal damper discs have inlet and outletplenum passageways extending therethrough which are defined by openingstherein. The alternate flowpaths between the heat exchanger platescomprise cross flow paths between said plenums and radial flow pathscommunicating with said central passageway. In this case, each of thethermal damper discs within the series thereof, is joined on one surfaceto the adjacent discby seam welding peripherally of both its inner andouter diameters and is joined on its opposite surface to the adjacentdisc by seam welding peripherally of the plenum defining openings.

Further, it is advantageous that the adjacent surfaces of the thermaldamper plates are disposed in substantially contiguous relationship toprevent a flow of fluid between the surfaces thereof. Also it ispreferable that the thermal damper plates adjacent the frame have athickness greater than those adjacent the heat exchanger plates.

In a more specific sense, the frame would have a conical annular seatthroughwhich the plenum opening passageways thereof extend. The thermaldamper plates would comprise a part of a thermal damper assembly whichincludes an annular mounting disc having a seat sealingly engaging theframe seat and also having corresponding plenum passageways or openingstherethrough. A thermal damper plate of intermediate thickness, insubstantially contiguous relationship with the mounting disc is joinedthereto by seam welding peripherally of the passageway openings thereof,successive thermal damper plates are then joined to the intermediateplate, first by seam welding around the inner and outer peripheriesthereof and then alternately by seam welding peripherally of the plenumdefining openings and the inner and outer diameters. Further, a heatexchanger disc is joined to the last of the thermal discs by seamwelding peripherally of the inner and outer diameters thereof. Thisassembly is completed by a support disc joined to the last of the heatexchanger discs by seam welding peripherally of the inner and outerdiameters thereof. The heat exchanger is completed by a series of heatexchanger discs in sub-stacks defined at their opposite ends by supportdiscs. This heat exchanger is then held in assembledrelation by tie rodsmeans which exert an axial loading on the stack of discs relative to theframe and compress same to bring the thermal damper discs or thesurfaces thereof into contiguous relationship.

Another aspect of the invention is found in a thermal mounting assemblyfor use in a heat exchanger as referenced above. This assembly comprisesa plurality of thermal damper discs having plenum passageway openingstherethrough. The discs are joined together in pairs by seam weldingperipherally of the openings therethrough. These pairs are divergentlyflared toward their inner and outer diameters which in turn are joinedperipherally thereof to adjacent pairs. By forming the thermal damper inthis fashion, the welding of the component parts thereof is facilitated.Further, the assembly described is characterized by the fact that whensubjected to an axial loading, the adjacent surfaces of the thermaldamper plates can be brought into contiguous relationship without anyundue stresses being induced therein.

The above and other related objects and features of the invention willbe apparent from a reading of the following description of a preferredembodiment thereof, with reference to the accompanying drawings, and thenovelty of the invention will be apparent from a reading of the appendedclaims.

In the drawings:

FIG. 1 is a longitudinal cross section of a heat exchanger in which thepresent invention is embodied;

FIG. 2 is a perspective view, partially exploded, of a stack of platescomprising the present heat exchanger;

FIG. 3 is a fragmentary perspective view, on a greatly enlarged scale,of a thermal damper assembly for the discs of the heat exchanger priorto installation in the heat exchanger; and

FIG. 4 is an enlarged longitudinal section of the thermal damperassembly of FIG. 3 after installation in the heat exchanger.

The heat exchanger illustrated in FIG. 1 and indicated by referencecharacter 10, is adapted for attachment to a gas turbine engine at apoint downstream of its last turbine stage. The engine itself may be ofconventional construction inaccordance with well known designs for aregenerative type engine. The hot gas discharge of the engine enters thecenter of the heat exchanger and then is directed radially outwardly,through a stack of plates, or discs, 1 1, to an exhaust system whichincludes a surrounding duct 12. The heat exchanger 10 comprises anadaptor frame 14 which may be attached to the load carrying structure ofthe engine.

The adaptor frame 14 has a plurality of passageways l6 and 18 whichrespectively connect with engine passageways (not shown) leading'fromthe engine compressor and leading to the engines combustor. Thecompressor passageways 16 are aligned with a plurality of inlet plenums20, see also FIG. 2, formed longitudinally through the stack of discs11. The combustor passageways 18 are aligned with a plurality of exitplenums 22 also extending longitudinally through the stack of discs 11.Radial flow paths for the hot gas discharge and cross flow paths,between adjacent plenums and 22, for the compressor air provide theprimary area of heat exchange. These flows are indicated in FIG. 2.

The heat exchanger 10 also comprises an end frame 24 and an end disc 26which define the downstream limit of the hot gas discharge flow path sothat all of the hot gasses may be turned radially outwardly through thestack of discs 11 and discharged to the duct 12. The frame 14 and 16 areconnected by tie rods 27 to hold the heat exchanger in assembledrelation.

The heat exchanger discs 11 have flanges peripherally of their inner andouter diameters which alternately project in opposite axial directionsso that the discs are disposed in pairs joined at their matchingflanges. The discs also have openings which respectively define theplenums 20 and 22. The pairs of discs joined at their flanges are thenjoined with the next adjacent discs by seam welding or the like,peripherally of the plenum defining openings thus forming a bellows typeof construction which defines the referenced flow paths for the radiallyflowing hot gas discharge and the cross flow of air from the inletplenums to the exit plenums. These discs are also corrugated, as in theabove referenced patent, for increased heat transfer as well as to provestructural strength when the stack of discs is subjected to axialloading through the tie rods 28.

The stack of discs 11 may be formed as a series of sub-stacks as taughtin U. S. Pat. No. 3,385,353 thus a plurality of discs 11 may be securedto somewhat thicker support discs 32 which also have correspondingplenums defining openings. The support discs 32 are slotted around theperipheries to receive rods 28 which extend between the frames 13 and24.

The stack of discs 11, or series of sub-stacks thereof, connect with theframe 14 through a thermal damper assembly 34 comprising in seriesrelationship (FIG. 4), a mounting disc 36, an intermediate thicknessdisc 38, a plurality of thermal damper discs 40, a pair of heat exchangediscs 11, and a support disc 32. The discs 36, 38 and 40 also haveopenings corresponding to and aligned with the openings in discs 11, tofurther define the plenums 20 and 22.

FIG. 3 illustrates the thermal damper assembly 34 prior to itsincorporation in the heat exchanger. The mounting disc 36 is flangedperipherally of its inner and outer diameters to form a seat forsealingly engaging a correspondingly shaped, annular seat on the frame14. The disc 36 is joined to the somewhat thinner, intermediatethickness thermal damper disc 38 by seam welding peripherally of theopenings defining the plenums 20 and 22. Successive pairs of the thinnerthermal damper discs 40 are also joined by seam welding peripherally oftheir plenum defining openings. Each pair of discs so joined at theiropenings is joined to the adjacent disc pair by seam weldingperipherally of their inner and outer diameters. The inner and outerdiameters of the disc pairs,joined at their openings, are divergentlyflared to facilitate seam welding of the inner and outer diameters ofadjacent pairs. The pair of discs 11 are also joined by seam weldingperipherally of their plenum defining openings and have divergentflanges to facilitate seam welding of their respective inner and outerdiameters to the last thermal damper disc 40 and the support disc 32.

When this assembly is incorporated in the heat exchanger, the discs 42are flattened by the compressive forces exerted through the tie rods 28.The flared thermal damper discs are sufficiently'thin that they are notunduly stressed when so flattened. The thermal damper discs thus havetheir opposite surfaces in contacting or substantially contiguousrelation so that there is no gas or air flow therebetween.

It will be apparent that when engine operation is initiated and allcomponents of the heat exchangers are at essentially the sametemperature, the heat exchange discs 11 will quickly increase intemperature and will be subject to a relatively rapid thermal growth.This is particularly reflected in the-discs ll of the mounting assembly.The disc 11 and the last thermal damper disc defines a relatively cool,air cross flow path, opposite which is radial flow path for the hot gasdischarge. The thermal growth of this disc 11 is then transferredthrough the succession of thermal damper discs 40 which providerespective increments of thermal growth as the heat transfers, or flowstherebetween. More specifically, since opposite sides of the thermaldamper discs are joined to adjacent discs by connections which arelaterally offset, i.e., between the inner and outer diameters and theplenum openings, an elongated heat flow path is created, there bieng arelatively low heat transfer between contiguous discs. This results inprogressive thermal growth of thethermal damper plates so that growthdifferentials between successive plates is relatively small and alsosmall between the thermal damper plate adjacent the frame M which is oflarge mass and heat sink with a relatively slow thermal growth. Thiseffect is further enhanced by forming the intermediate disc 40 and themounting disc 33 of progressively greater thickness. The net effect ofthe de scribed thermal damper assembly is to greatly minimize inducedstresses between adjacent discs which tend to rupture the jointstherebetween. This all combines to provide an economical mounting of theheat exchanger which minimizes the possibilities of failure and greatlyprolongs its service life.

While a preferred embodiment of the invention has been described,modifications thereof will be apparent to those skilled in the artwithin the broader aspects of the invention. Thus, for example, in thebroader aspects of the invention, the thermal damper plates may not beincorporated in a separate assembly or may be joined by other weldingprocedures such as brazing or the discs may take other plate form. Thespirit and scope of the invention is therefore to be derived from thefollowing claims.

Having thus described the invention, what is claimed is novel anddesired to be secured by letters of patent of the United States is:

l. A heat exchanger comprising a series of relatively thin heat exchangeplates which define alternate flow paths for different fluids betweenwhich heat energy is to be exchanged,

a frame of relatively large mass and low rate of thermal growth,

a thermal mounting interposed between said frame and series of heatexchange plates, said mounting including a series of successivelyconnected, thermal damper plates with the connections between eachthermal damper plate within the series thereof being laterally spaced onopposite sides thereof.

2. A heat exchanger as in claim 1 wherein said thermal damper plates aredisposed with their adjacent surfaces in substantially contiguousrelation.

3. A heat exchanger as in claim 2 wherein thermal damper plates adjacentthe frame have a thickness greater than the thermal damper platesadjacent said heat exchanger plates.

4. A heat exchanger as in claim ll wherein the heat exchanger plates andthe thermal damper plates are annular discs and define a centralpassageway for one of said fluids,

the frame, the heat exchanger discs, and the thermal damper discs haveinlet and outlet plenum passageways extending therethrough, defined byopenings therethrough, and the alternate flow paths, between said heatexchange discs, comprise cross flow paths between said plenums andradial flow paths communicating with said central passageway and furtherwherein each thermal damper disc, within the series thereof, is joinedon one surface to the adjacent disc by seam welding peripherally of bothits inner and outer diameters and is joined on its opposite surface tothe adjacent disc be seam welding peripherally of said plenum definingopenings.

5. A heat exchanger as in claim 4 wherein the adjacent surfaces of saidthermal damper discs are disposed in substantially contiguousrelationship thereby preventing a flow of fluid between the surfacesthereof.

6. A heat exchanger as in clain 5 wherein the thermal damper discsadjacent the frame are thicker than those adjacent the heat exchangerplates.

7. A heat exchanger as in claim 6 wherein the frame has a conicalannular seat through which said plenum passageways extend,

the thermal mounting is in the form of an assembly comprising, in seriesrelationship,

an annular mounting disc having a correspondingly formed seat forsealingly engaging said frame seat and also having corresponding plenumpassageways therethrough,

an intermediate thickness, thermal damper disc in substantiallycontiguous relationship therewith and joined thereto by seam weldingperipherally of the openings thereof,

a first, thin thermal damper disc joined to the intermediate disc byseam welding peripherally of the inner and outer diameters thereof,

a plurality of thinner thermal damper discs,

a plurality of heat exchange discs, the first of which is joined to theadjacent thermal damper disc by seam welding peripherally of their innerand outer diameters, and a support disc joined to the last heatexchanger plate by seam welding peripherally of the inner and outerdiameters thereof,

further heat exchange discs arranged in sub-stacks bounded by end platesand means holding said assembly in compressed relation.

8. A thermal mounting assembly comprising a plurality of annular,thermal damper discs having aligned passageway openings therethrough andspaced around the central opening thereof,

said discs being disposed in series stacked relation,

successive pairs of discs being joined by seam welding around saidopenings with their inner and outer diameters being divergently flaredand adjacent pairs of discs being joined by seam welding around theirinner and outer diameters, the divergence of the diameters facilitatingthe welding thereof said stack of discs being further characterized bythe thinness of the discs permitting their flattening into substantiallycontiguous surface relation, without undue deflective when the stesses,stack is subject

1. A heat exchanger comprising a series of relatively thin heat exchangeplates which define alternate flow paths for different fluids betweenwhich heat energy is to be exchanged, a frame of relatively large massand low rate of thermal growth, a thermal mounting interposed betweensaid frame and series of heat exchange plates, said mounting including aseries of successively connected, thermal damper plates with theconnections between each thermal damper plate within the series thereofbeing laterally spaced on opposite sides thereof.
 2. A heat exchanger asin claim 1 wherein said thermal damper plates are disposed with theiradjacent surfaces in substantially contiguous relation.
 3. A heatexchanger as in claim 2 wherein thermal damper plates adjacent the framehave a thickness greater than the thermal damper plates adjacent saidheat exchanger plates.
 4. A heat exchanger as in claim 1 wherein theheat exchanger plates and the thermal damper plates are annular discsand define a central passageway for one of said fluids, the frame, theheat exchanger discs, and the thermal damper discs have inlet and outletplenum passageways extending therethrough, defined by openingstherethrough, and the alternate flow paths, between said heat exchangediscs, comprise cross flow paths between said plenums and radial flowpaths communicating with said central passageway and further whereineach thermal damper disc, within the series thereof, is joined on onesurface to the adjacent disc by seam welding peripherally of both itsinner and outer diameters and is joined on its opposite surface to theadjacent disc be seam welding peripherally of said plenum definingopenings.
 5. A heat exchanger as in claim 4 wherein the adjacentsurfaces of said thermal damper discs are disposed in substantiallycontiguous relationship thereby preventing a flow of fluid between thesurfaces thereof.
 6. A heat exchanger as in clain 5 wherein the thermaldamper discs adjacent the frame are thicker than those adjacent the heatexchanger plates.
 7. A heat exchanger as in claim 6 wherein the framehas a conical annular seat through which said plenum passageways extend,the thermal mounting is in the form of an assembly comprising, in seriesrelationship, an annular mounting disc having a correspondingly formedseat for sealingly engaging said frame seat and also havingcorresponding plenum passageways therethrough, an intermediatethickness, thermal damper disc in substantially contiguous relationshiptherewith and joined thereto by seam welding peripherally of theopenings thereof, a first, thin thermal damper disc joined to theintermediate disc by seam welding peripherally of the inner and outerdiameters thereof, a plurality of thinner thermal damper discs, aplurality of heat exchange discs, the first of which is joined to theadjacent thermal damper disc by seam welding peripherally of their innerand outer diameters, and a support disc joined to the last heatexchanger plate by seam welding peripherally of the Inner and outerdiameters thereof, further heat exchange discs arranged in sub-stacksbounded by end plates and means holding said assembly in compressedrelation.
 8. A thermal mounting assembly comprising a plurality ofannular, thermal damper discs having aligned passageway openingstherethrough and spaced around the central opening thereof, said discsbeing disposed in series stacked relation, successive pairs of discsbeing joined by seam welding around said openings with their inner andouter diameters being divergently flared and adjacent pairs of discsbeing joined by seam welding around their inner and outer diameters, thedivergence of the diameters facilitating the welding thereof said stackof discs being further characterized by the thinness of the discspermitting their flattening into substantially contiguous surfacerelation, without undue deflective when the stesses, stack is subject toan axial loading.